Bridges for piano



Sept. 23, 1969 TSUNEQ s zu ET AL 3,468,207

BRIDGES FOR PIANO Filed Dec. 23, 1966 2 Sheets-Sheet 1 f J f n J i Ik L Wm WM 26M 4 WM W INVENTORj Sept. 23, 1969 TSUNEO SUZUKA ET AL 3,468,207

BRIDGES FOR PIANO Filed Dec. 23, 1966 2 Sheets-Sheet 2 BY W INVENTOR. I

United States Patent 3,468,207 BRIDGES FOR PIANO Tsuneo Suzuka and Haruhisa Noda, Hamamatsu-shi, Japan, assignors to Nippon Gakki Seizo Kabushiki Kaisha, Hamamatsu-shi, Japan Filed Dec. 23, 1966, Ser. No. 604,205 Claims priority, application Japan, all Dec. 29, 1965 (utility models), 40/108,243, 40/ 108,244, and 40/108,245; Feb. 11, 1966, 41/ 8,014

Int. Cl. Gc 3/04 U.S. Cl. 84209 4 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to bridges secured on the sounding board of a piano, and more particularly, to an improved structure of a piano bridge which can transmit the vibrations of strings to the piano sounding board in such a manner that the individual sounds are well balanced with one another over the entire gamut of the piano musical sounds.

Usually, a bridge for a piano is a long wooden member having a square or rectangular cross-section, and is securely attached to the sounding board obliquely with respect to the key board by such means as an adhesive agent or dowels. The bridge supports strings on the upper surface and the vibrations of the strings generated by striking piano keys are transmitted to the sounding board through the bridge. In large-size grand pianos of full or semi-concert type a single bridge is used which has a bent portion located remote from the key board, while smallsize, grand pianos or upright pianos use two bridges, namely, a long bridge and a short bridge, for reasons of the metal frame structure. In either case, the most important role to be played by the bridge is to support the strings in predetermined positions so that vibrations of proper tones may be generated and to transmit vibrations of the strings to the sounding board which amplifies and radiates the transmitted vibrations.

The vibration transmitting characteristics of the bridge should be uniform for string vibrations of different frequencies, and especially in middle and treble regions. The disparity of transmission of vibrations of individual strings brings forth differences in volume and quality of sounds of different regions, so that good quality sound, particularly beautiful chords, cannot be obtained.

In order to provide uniform volume and quality of sounds of bass and middle regions on the one hand, and sounds of treble region on the other hand, the usual bridge has a configuration such that the height is less towards the treble region in order to transmit the vibrations of the treble region strings with as little attenuation as possible. By way of example, an ordinary bridge for a grand piano has a height of about 35 mm. at the highest tonal region, the height progressively increasing toward the bass region to about 45 mm. at the lowest tonal region. With a bridge of such a construction an improvement of sound in the treble region is accompanied by some sacrifice of sounds in the middle region, which ice are required to sound best during the piano performance, for the sake of the tonal balance with the treble tone region.

The vibrations transmitted to the bridge should further be transmitted to the sounding board uniformly through the entire longitudinal portions of the bridge. The sounding board is provided on its under side with a plurality of spaced parallel ribs disposed substantially at right angles with the bridge. Consequently, the rigidity of the sounding board differs along the bridge between portions on which the rib is present and portions on which the rib is absent. The result is that the sound of some tones is different from that of other tones.

A basic object of this invention is to provide a bridge capable of effectively transmitting vibrations of strings to the sounding board, so that the volume and quality of sounds may be greatly improved.

Another object of this invention is to provide a bridge which can permit a uniformity in the sounds of the tones over the entire sound gamut.

A further object of this invention is to provide a sounding board assembly (this term includes a sounding board, ribs and bridges) including long and short bridges for use in small-size pianos, whereby the tone sounds are well balanced between those sounds generated by strings in contact with the long bridge and those generated by strings in contact with the short bridge.

These and other objects of this invention will be more fully understood from the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of a sounding board provided with one embodiment of the bridge according to this invention;

FIG. 2 is an enlarged cross section taken along line II-II of FIG. 1;

FIG. 3 is a side view, partly in section, illustrating another embodiment of the bridge attached to the sounding board in accordance with this invention;

FIG. 4 is a side view, partly in section, illustrating a further embodiment of the bridge according to this invention;

FIG. 5 is a plan view illustrating one embodiment of the sounding board assembly according to this invention;

FIG. 6 is a bottom view of the assembly shown in FIG. 5;

FIG. 7 is a section taken along line VII-VII of FIG. 5; and

FIG. 8 is a section similar to FIG. 7 illustrating another embodiment of the sounding board assembly in accordance with this invention.

In the drawings same or corresponding parts are designated by like reference numerals.

Referring to the drawings, and particularly to FIG. 1, a sounding board 10 for a full concert type grand piano has on its under side a plurality of ribs 11 and on its upper side a bridge 12 comprising a long bridge section 12a and a short bridge section 12b convected by a slender member disposed therebetween secured thereto by means of an adhesive agent and/ or dowels.

The bridge 12 is provided with longitudinal grooves 13, one on each side. The grooves 13 extend from the neighborhood of the end of the treble region into the middle region and terminates at about one third of the length of the longer portion of the bridge from the outermost point of the acutely bent portion.

The grooves 13 are substantially semi-circular in cross section and disposed approximately in the middle of the height of the bridge 12, as is clear from FIG. 2. It is preferable that the groove have an arcuate cross section having a suitable curvature depending upon the shape and dimensions of the bridge. The depth of the grooves is selected within a range leaving a rest portion having a thickness suflicient for retaining the mechanical strength of the bridge, usually, the thickness of about a half the width of the bridge. The depth of the groove therefor is at least one sixth, preferably a quarter the lateral dimension of the bridge.

The vibration generated when one of the strings affixed under tension with well-known pins installed on the bridge, is hammered by striking a corresponding piano key, is transmitted through the bridge to the sounding board. In this instance the vibration generated when strings located on the grooved portion of the bridge 12 are hit by a hammer is transmitted to the sounding board very effectively. One of the reasons for the effective transmission of the vibration is thought to lie in the fact that the existence of the grooves 13 considerably reduce the vertical rigidity of the bridge 12 without causing any change in the state of connection between the string and the bridge and between the bridge and the sounding board, so that the vibration of the string is transmitted to the sounding board without attenuation by the bridge. Such an improvement in the vibration transmitting characteristics is supposed to be more remarkable for higher frequencies under the general rules in acoustics. Thus, a piano using the bridge 12 having the grooves 13 extending over the middle tone region and into a portion of the treble tone region can afford improved tonal quality, good balance of middle and treble tones, and beautiful chords consisting of notes in both regions, as not only the sounding of tones in the middle region is considerably improved but also higher frequency components of the middle region tones are effectively amplified. The grooves 13 may extend continuously or intermittently from the treble region into the bass region according to the size and material of the sounding board and the thickness of the strings. The bridge having these grooves may be applied to all types of pianos.

FIG. 3 illustrates a bridge structure which is similar to the structure shown in FIGS. 1 and 2 having grooves 13 but which is further provided with recesses 14 having sufficiently longer length than the width of the ribs 11 formed in the lower side and adapted to be positioned above ribs 11, thus leaving clearances between the bridge and the sounding board. The portions 15 between adjacent recesses 14 are in contact with the sounding board 10 and secured thereto by the agency of bushings 16 and wood screws 17. Connecting pins 18 are inserted through ribs 11, sounding board 10 and recesses 14 into the bridge 12. The recesses 14 may be provided along the entire length of a portion, preferably over the middle region up to the curved portion, of the bridge 12 at positions where the bridge 12 crosses the ribs 11 beneath the sounding board 10.

As the above bridge 12 is attached to the sounding board 10 at portions other than the portion provided with the rib 11 at the back, vibrations transmitted to the bridge 12 at different portions thereof may further be transmitted to the sounding board 10 in a uniform way without being influenced by the difference in rigidity of the bridge 12 between portions where there is the rib 11 beneath and portions where there is no rib beneath. Further, the effective transmission of the vibration to the sounding board 10 is assured by the provision of the connecting pins 18 which pass the rib 11 and the sounding board 10 and extend into the body of the bridge 12 through the space of the recess 14.

The provision of the recesses in the bridge at portions where the rib is present beneath is known in the art. With this structure, however, the transmission of vibrations is effected only to the portions of the sounding board where the rib is absent, so that the vibration of the bridge can not be sufficiently transmitted to the sounding board unless the disparity of the transmission of vibration is alleviated. Such a loss in the transmission of vibrations is as undesir- 4 able as the disparity of the transmission in pursuit of good sounding.

The bridge shown in FIG. 4 is provided with one or more lateral cuttings indicated at 19 in addition to the longitudinal grooves 13. The cutting 19 has a depth about one third to a half the height of the bridge 12, and its inner edge is made to have an enlarged cylindrical shape so as to prevent the formation of undesirable cracks into the body of the bridge 12. These cuttings 19 are preferably located such that they divide the entire length of the bridge 12 into a few portions of equal length. The existence of the cuttings 19 aids in reducing the rigidity of the bridge 12 Without affecting its vibration responsive charactcristics to enable transmission of vibrations to the sounding board with a minimum of attenuation, so that these cuttings are very effective in achieving good transmission of vibrations in combination with the grooves 13.

The width of the cutting 19 should be very small, for instance less than one millimeter and preferably less than 0.5 mm. to minimize the decrease in the contact area, hence the decrease in the firmness of connection, between the bridge 12 and the'sounding board 10 and to minimize the disparity of transmission of vibrations. Further, these cuttings facilitate vertical bending of the bridge such that the bridge may be brought into close contact along its entire length with the upper surface of the sounding board, so that the vibration of the bridge may be transmitted to the sounding board more efficiently.

FIG. 5 shows a sounding board 10 for a grand piano and provided withtwo bridges, a long bridge 12a to support strings in treble and middle regions and a short bridge 12b to support strings in bass region with the long bridge being provided with longitudinal grooves as described above on both sides. At the back of the sounding board, there is provided a connecting member 21 connecting one end of both the long and short bridges 12a and 1212, as shown in FIG. 6.As is apparent from FIG. 7, the connecting member 21 is connected at its one end to the corresponding end of the long bridge 12a and at its other end to the corresponding end of the short bridge 12b respectively through the sounding board 10 by such connecting means as wood screws 22. The connecting member 21 may be either spaced from the sounding board 10 at the central portion as shown in FIG. 7 or in contact with the sounding board 10, such as at 21a in FIG. 8.

With this bridge structure comprising long and short bridges 12a and 1212 which are connected to each other by means of connecting member 21, the vibration of strings on one bridge is also transmitted to the other bridge, thus uniformly vibrating the sounding board, as is done with a single curved bridge which can be adapted only for a large-size grand piano. Accordingly the sounding of tones generated from strings supported on both the bridges is uniformalized, so that the balance of sounds over the entire gamut may be obtained for small-size grand pianos and upright pianos as for large-size grand pianos. It will be apparent that this uniformity of sounding is further promoted by the provision of the above described grooves 13.

It is to be understood that the foregoing description of specific examples of this invention is made by way of example only and is not to be considered as a limitation on its scope.

What is claimed is:

1. A bridge for pianos having longitudinal grooves extending along opposite sides of said bridge wherein said bridge has one or more lateral cuttings cut into the body of said bridge from its under side and having a depth of at least one third the height of said bridge, said cuttings dividing the entire length of said bridge into portions having an equal length.

2. A sounding board assembly comprising a sounding board provided on its back side with a plurality of ribs, a bridge having longitudinal grooves extending along opposite sides thereof and recesses formed in the lower side thereof in portions where the rib is present beneath, and means connecting said bridge and said rib at portions where said recesses are present.

3. A sounding board assembly according to claim 2 wherein said bridge is for supporting piano strings which provide musical tones of the bass, middle and treble regions of the musical scale which strings are sequentially supported by said bridge and said recesses are located in that portion of said bridge which supports the middle region strings.

4. A sounding board assembly for pianos comprising a sounding board provided on its back side with a plurality of ribs, a bridge structure including a short bridge and a long bridge which is provided with longitudinal grooves extending along opposing sides thereof, said bridges being 15 secured on the upper side of said sounding board, and a connecting member connecting adjacent ends of said long and short bridges and arranged on the under side of said sounding board.

References Cited UNITED STATES PATENTS 662,521 11/1900 Butler 84-212 FOREIGN PATENTS 529,517 9/ 1921 France.

RICHARD B. WILKINSON, Primary Examiner JOHN F. GONZALES, Assistant Examiner 

